Step By Step - Installing a new hard drive

Originally published in Australian Personal Computer Magazine, November 1997.
Last modified 03-Dec-2011.


Hard disk prices are plunging and a new drive is a more tempting proposition every day. But adding a second hard drive to an IBM compatible machine has historically been the source of many nightmares. It doesn't have to be difficult, though. If you've got a recent computer and you're adding a current model hard drive, much of the exciting complexity of the bad old days melts away.

A new hard drive will either be a replacement for an older drive, or an addition. And the drive interface, in a PC clone, will nowadays almost certainly be EIDE (Enhanced Integrated Drive Electronics) or the older IDE (Integrated Drive Electronics). For simplicity's sake, I'll say "IDE" when I mean IDE/EIDE for the rest of this tutorial, because the differences aren't likely to be apparent in domestic circumstances. If you're one of the rebels with a SCSI controller, adding more drives is even easier.

Preparing the drive

Any IDE controller can handle two hard drives at once. IDE drives actually have the controller built right onto the drive - the card plugged into the PC expansion slot, is really little more than a cable adaptor, with no controller circuitry of its own. For all remotely recent motherboards, the IDE connection circuitry is built into the motherboard, and no adaptor card is needed; you just have IDE cable sockets right there on the motherboard.

Multiple IDE controllers, however, cannot coexist in the system, so dual IDE drives have to be configured as a "master" and a "slave" - the slave drive has its own controller deactivated, and is operated by the controller on the master drive. The fastest drive should be the master, because it probably has the best controller.

The older the drive, the more cryptic the master/slave configuration process is likely to be. Configuration is done with jumpers - those little plastic blocks with a copper clip inside that slide over pairs of pins to make electrical connections. If you have the paperwork for your hard drives, you should have no trouble setting the one or two jumpers needed on each drive. If not, manufacturers' Web sites are often helpful, and in extremis a phone call to the local representative should get you a data sheet on any recent drive.

SCSI setup

SCSI drives have more jumpers than IDE, unless they're the new and spiffy devices that can set their own addresses. With a combination of jumpers, you specify SCSI address 0 to 7 for the drive, and there should also be a termination jumper or receptacles for terminating resistor packs. Each end of a SCSI chain must be terminated; if you have only internal or only external drives, the controller is one end and the device physically at the other end of the cable needs to be terminated. With a combination of internal and external devices, the controller must be unterminated and the devices at each end terminated.

Popping the top

Opening your computer can be an easy or an annoying task, depending on the case design. Most clones use several Phillips head screws to hold the case on, but some have other screws, plastic clips, security locks and more. Remember to leave the computer plugged in, but turned off - this means the mains earth will still be connected to the computer chassis, which makes it impossible for the computer to develop a static charge which could earth itself through you. To get rid of any static you may be carrying, simply touch the case of the power supply after you open the machine, and touch it again if you've moved away from the computer. Remember - a static charge as small as 200 volts, which you won't even feel, can destroy chips and spoil your whole day.

Plugging it in

IDE drives have a 40-pin connector, which on classier drives is surrounded by a plastic rim with a slot cut out of it - a "keyed" connector - which with a matching cable makes it impossible to connect the drive the wrong way. If your cable isn't keyed, you can plug it in upside down; if there's no rim around the connector, it's possible to plug the cable in off-centre, so that two or more pins aren't connected and all the rest are wrong. Pin one on the drive will be on the left hand side of the connector as you look at the back of the drive (there's sometimes microscopic numbering stamped on the plastic around the pins); the cable should have a stripe on wire number 1, so you just line up the stripe end with pin 1, make sure the plug's aligned with the whole connector, and push. You will, of course, need a cable with sufficient connectors on it.

Internal SCSI drives use a 50 pin connector, to which all of the above applies. External SCSI devices use a marvellous assortment of DB25, 50 way Centronics and new super-high-density connectors, possibly because of a conspiracy on the part of the makers of adaptor cables.

Hard drive power connectors are almost exclusively the standard four pin Molex type, renowned for their one-in-three ability to practically weld themselves together. If unplugging a seized Molex connector, be patient and as gentle as you can, because the receptacle on the drive is usually only held on by its four solder joints.

Setting up

Now you have to tell the computer's BIOS about the new hardware, and save the new configuration. If you've replaced your old boot drive, you won't be able to access it until you tell the BIOS about the new drive. If you've added a new drive and left the old boot drive as well, the machine will boot fine without being told about the new hardware, but the new drive will be inaccessible.

Modern PCs make the drive identification process simpler, because they can actually read the relevant settings from the drives. Any remotely current machine will, at a bare minimum, have a "user defined" drive type that lets you type in the numbers yourself, saving you from the old nightmare of fitting your drive to one of the 47 "drive types" the BIOS knew about.

Go to your machine's BIOS setup page (canonically, by holding the delete key while booting), select the drive setup page, and use the "read settings from drive" option or, if that doesn't work or isn't available, enter the number of cylinders, heads and sectors, and the number of the first write precompensation cylinder, if one is specified. If you're using nothing but SCSI drives, you should set the BIOS drive identification info to "no hard drive". Your SCSI controller ought to automatically try to boot from a drive with the ID number 0.

You may have vague memories in your head of a process called a "low-level format". Ignore these memories. No modern drive needs to be low level formatted by the user, which is just as well because practically no modern drives actually CAN be, although many will accept a low-level format command, simply erase all of their data, and then report that the format is complete.

Carving it up

Now that you've got a drive that's recognised by the system, it's time to partition.

Partitioning a drive can divide it into what looks to your operating system like several separate drives, adding up to the full capacity of the drive, or can leave it as one device. For almost all intents and purposes you can treat different partitions as whole different drives.

The details of partitioning and the different formats possible for DOS and Windows, Windows 95 Release 2, OS/2 and Linux are too complex for the space available here, so sticking with the "plain vanilla" approach, let's just look at Windows 95 drive partitioning, using FDISK from DOS.

Older versions of Windows 95 support only the FAT16 drive format, which uses space less and less efficiently as the size of a drive gets bigger and cannot be used on partitions bigger than two gigabytes. On the plus side, FAT16 drives are readable by older versions of Windows and DOS, and work will all the hard drive compression, optimisation, backup and repair software.

FAT32 is a new format for Windows 95 Release 2 - the version that's come on all new machines for a while now, but is not legally available by itself - which uses space more efficiently. FAT32 partitions can hold more data per formatted megabyte than FAT16, and the smaller the average size of your files, the better their advantage. On the other hand, you can't compress FAT32 partitions (yet), only the newer disk utility software supports them, and older versions of Windows can't read them.

FDISK automatically asks you whether you want to enable FAT32 when it detects a hard drive larger than 512Mb; it cannot create FAT32 partitions smaller than 512Mb.

For a straight Win 95 installation, the partition you want to boot from must be a "Primary DOS Partition", and any other partitions should be of the Extended variety. Make your partitions and reset the computer; now you just have to format whatever partitions you've made by typing "format <drive letter>" from DOS, and you're ready to start filling them with software - or installing an operating system.

In order to reinstall Windows 95 on a machine with a correctly partitioned and formatted, but empty, boot drive, you need the floppy version of 95 (and a great deal of spare time) or a floppy boot disk with a CD-ROM driver on it and config.sys set up to run the driver and make the CD-ROM accessible, whereupon you simply run the Windows setup program. There's an option to make such a boot disk included in the extra software that comes with many computers; if no such easy fix is available, you'll need the right driver, and can either download it from somewhere and set the thing up yourself or, better, nag the supplier of your computer to give you what you should have got already.

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